Curved eye protection shield for welding protection

ABSTRACT

A curved eye protection shield for welding protection. The eye protection shield has an electrically switchable darkening filter and a protective cover. The darkening filter has eye facing major inner and outer surfaces, and the protective cover has major inner and outer surfaces. The protective cover is provided for arrangement on the inner surface of the darkening filter. The inner and outer surface of the darkening filter are equidistant, whereas the inner and outer surface of the protective cover are non-equidistant. The invention is advantageous in that it provides an eye protection shield having a minimized refractive power.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/098,155, filed Nov. 1, 2018, now allowed; which is a US 371application of International Application No. PCT/US2017/030344, filedMay 1, 2017; which claims priority to EP Application Serial No.16168229.9, filed May 1, 2016, the disclosures of which are incorporatedby reference in their entirety herein.

FIELD OF THE INVENTION

The invention relates to a curved eye protection shield for weldingprotection, and in particular to a curved eye protection shield whichcomprises an electrically switchable darkening filter having twoequidistant major surfaces, and a protective cover having twonon-equidistant major surfaces.

BACKGROUND ART

Automatic darkening filters commonly have a switchable filter thatautomatically changes from a light-transmission-state to adark-transmission-state in response to incident light. The switching isgenerally achieved through use of a photodetector that is located on, oras part of, personal protective equipment. The photodetector recognizesthe presence of the incident light-to-be-filtered, and an electronicmodule generates a control voltage that, when applied to the switchablefilter, causes the filter to change from the light-transmission-state tothe dark-state.

Automatic light filters have been designed which contain liquid-crystalcells located between polarizing films. U.S. Pat. No. 4,240,709 toHornell describes a switchable filter that has a single-twisted,nematic, liquid-crystal cell sandwiched between a pair of mutuallycrossed polarizers. The liquid-crystal cells are optically-transparentglass substrates that include transparent electrode and alignmentlayers. The liquid-crystal molecules orientate themselves in aparticular direction when a voltage is applied across the liquid-crystalcell under the control of an electronic module. Many commerciallyavailable products use this kind of switchable filter.

The use of an automatic-darkening filter in a protective shield givessignificant ergonomic benefits. Previously welders, for example, had to“nod” their welding shield down when they struck the welding arc toensure that their eyes were protected from the torch light. Automaticwelding filters eliminate this action since the welding shield can beleft in position continuously.

SUMMARY OF THE INVENTION

The invention relates to a curved eye protection shield for weldingprotection. The eye protection shield comprises an electricallyswitchable darkening filter and a protective cover. The darkening filterhas an eye facing major inner surface and a major outer surface. Theinner surface and the outer surface of the darkening filter are oppositeof each other, meaning facing in opposite directions. Further, theprotective cover has a major inner surface and further a major outersurface. The inner surface and the outer surface of the protective coverare opposite of each other, meaning facing in opposite directions. Theprotective cover may be arranged relative to the darkening filterdirectly on or spaced adjacent the outer surface of the darkeningfilter, or on or spaced adjacent the inner surface of the darkeningfilter. Accordingly, the outer surface of the protective cover faces theinner surface of the darkening filter or, alternatively, the innersurface of the protective cover faces the outer surface of the darkeningfilter. The inner and outer surface of the darkening filter areequidistant, whereas the inner and outer surface of the protective coverare non-equidistant. The electrically switchable darkening filtertherefore has two equidistant major surfaces, and the protective coverhas two non-equidistant major surfaces.

Because the inner and outer surface of the darkening filter beingequidistant the portion of the darkening filter formed by the inner andouter surface has a uniform thickness (defined between the inner andouter surface of the darkening filter). Further, because the inner andouter surface of the protective cover being non-equidistant the portionof the protective cover formed by the inner and outer surface has anon-uniform thickness (defined between the inner and outer surface ofthe protective cover).

The invention is advantageous in that it provides for a curved eyeprotection shield having no or a minimized refractive power. Further,the invention allows for compensating a refractive power of a curveddarkening filter. The invention further provides for a maximizedconvenience for a wearer of a welding protector having a curveddarkening filter, in providing an eye protector with minimizedrefractive power.

For the purpose of the present specification the term “equidistant”refers to two curves or surfaces which extend at the same distancerelative to each other along their length or across their areas,respectively. For example, two equidistant planes are parallel to eachother.

Preferably the darkening filter is switchable between alight-transmission-state in which a substantial portion of light canpass through the darkening filter and a dark-state in which asubstantial portion of light is blocked from passing through thedarkening filter. In the light-transmission-state the transmittance ofthe darkening filter may be within a range of about 1% to about 20%, inmore particular within a range of about 5% to about 10%, whereas in thedark-state the transmittance of the darkening filter may be within arange of about 0,0005% to about 0.1%.

In one embodiment the inner and outer surface of the darkening filterare cylindrical and concentric relative to each other. The inner andouter surface of the darkening filter preferably form surfaces of aportion of the darkening filter which serve for the user, for example awelder, to see through during use. This portion of the darkening filtertherefore may also be referred to as the “see-through portion of thedarkening filter”. The darkening filter may have further portions, suchas one or more structures for stiffening the darkening filter or formounting the darkening filter within the eye protection shield, forexample. Such further portions are typically not used for seeing throughand further may not have equidistant inner and outer surfaces.

Preferably, the inner and outer surface of the protective cover arecylindrical. However, the cylinder shape of both, the inner and outersurface of the protective cover, are preferably in an off-centerrelationship to each other. The cylindrical shape of the inner and outersurface of the protective cover may have the same radius. Again, theinner and outer surface of the protective cover preferably form surfacesof a portion of the protective cover which serve for the user, forexample a welder, to see through during use. This portion of theprotective cover therefore may also be referred to the “see-throughportion of the protective cover”. The protective cover may have furtherportions, such as one or more structures for stiffening the protectivecover or for mounting the protective cover within the eye protectionshield, for example. Such further portions are typically not used forseeing through.

In a further embodiment the protective cover is pre-shaped so that theouter surface of the protective cover corresponds in shape to the innersurface of the darkening filter. Further, the protective cover may bepre-shaped so that the outer surface of the protective cover correspondsto a proportionally reduced shape of the inner surface of the darkeningfilter. Such a proportionally reduced shape may be provided to accountfor a space between the darkening filter and the protective cover. Forexample, the radius of the outer surface of the protective cover may besmaller than the radius of the inner surface of the darkening filter.Further, the darkening filter and the protective cover may be arrangedrelative to each other such that the inner surface of the darkeningfilter and the outer surface of the protective cover are concentric.Accordingly, the space between the inner surface of the darkening filterand the outer surface of the protective cover has a uniform thickness.

In an alternative embodiment, the protective cover is pre-shaped so thatthe inner surface of the protective cover corresponds in shape to theouter surface of the darkening filter. Further, the protective cover maybe pre-shaped so that the inner surface of the protective covercorresponds to a proportionally enlarged shape of the outer surface ofthe darkening filter. Such a proportionally enlarged shape may beprovided to account for a space between the darkening filter and theprotective cover. For example, the radius of the inner surface of theprotective cover may be greater than the radius of the outer surface ofthe darkening filter. Further, the darkening filter and the protectivecover may be arranged relative to each other such that the outer surfaceof the darkening filter and the inner surface of the protective coverare concentric. Accordingly, the space between the outer surface of thedarkening filter and the inner surface of the protective cover has auniform thickness.

For example, the protective cover may be molded (for example injectionmolded) from an optically clear plastic material. The inner and outersurface of such a molded protective cover preferably naturally has thecylindrical shape, in particular without being under mechanical tension.

In one embodiment the protective cover has a first thickness adjacent amargin and a second thickness in the middle between two oppositemargins. The margins preferably refer to lateral margins of thesee-through portion. The lateral ends of the see-through portion areopposite ends in a horizontal dimension of the eye protection shield.The term “horizontal” refers to a dimension of the eye protection shieldthat is defined by a parallel to the centers of the wearer's eyes, whenthe eye protection is worn by a wearer. Further the eye protectionshield has a vertical dimension. The term “vertical” refers to adimension perpendicular the horizontal dimension and perpendicular tothe optical axis of the wearer's eyes in a straight view orientation.The first and second thickness each are preferably uniform along thevertical dimension.

The second thickness is preferably greater than the first thickness. Thethickness of the protective cover gradually increases from the firsttoward the second thickness. The second thickness may be within a rangeof about 1 mm to 3 mm, preferably 1.7 mm or about 1.7 mm.

In one embodiment the cylindrical shape of the inner and outer surfaceof the protective cover are based on the same radius. The radius may bewithin a range of 70 mm to 150 mm, more preferably within a range of 80mm to 100 mm, most preferably 85 mm or about 85 mm. Further, the centeraxes of the cylindrical shape of each the inner and outer surface of theprotective cover are preferably parallel offset from each other on anormal on the inner and outer surface. Preferably the offset is within arange of 0.5 mm to 3 mm, more preferably 1.7 mm or about 1.7 mm.

In one embodiment the protective cover is removably attached to thedarkening filter. The darkening filter and the protective cover arepreferably arranged with a (preferably uniform) space between the innersurface of the darkening filter and the outer surface of the protectivecover. Alternatively, the darkening filter and the protective cover arearranged with a (preferably uniform) space between the outer surface ofthe darkening filter and the inner surface of the protective cover. Theeye protection shield may comprise a spacer for providing such a space.The spacer may be formed by one or more protrusions (for example acircumferential rim or circumferentially distributed pins) that is/arearranged adjacent a margin of the inner or outer surface of thedarkening filter or adjacent a margin of the inner or outer surface ofthe protective cover. Further, the protective cover may be mounted in awelding protector in which also the darkening filter is integrated. Theprotective cover may in this embodiment mounted at a space relative tothe darkening filter. Alternatively, the darkening filter and theprotective cover may, for example, be bonded to each other by anoptically clear adhesive.

For the purpose of the present specification any surface of the spacerdoes not form part of the inner or outer surface of the darkening filterand/or the protective plate, although the spacer may be monolithicallyformed with the darkening filter and/or the protective cover.

In one embodiment the protective cover is made of a plastic materialselected from among polycarbonate (PC), polymethyl methacrylate (PMMA),polystyrene (PS) and styrene acrylonitrile copolymer (SAN). Preferably,the protective cover is molded, in particular injection molded, in thecylindrical shape. In more particular, the protective cover may bemolded, in particular injection molded, such that the inner and outersurface are in the cylindrical shape. In a further embodiment thedarkening filter comprises liquid crystals arranged in direct contactbetween a first and second alignment layer, the first and secondalignment layer being arranged on a first and a second transparentelectrode layer, respectively, and the first and second transparentelectrode layer are arranged on a first and a second transparent layer,respectively, and wherein the first and a second transparent layer areeach provided with a polarizer. The first and second transparent layer,first and second electrode layer and first and second alignment layerform a liquid crystal cell. In a preferred embodiment the eye protectionshield comprises two liquid crystal cells arranged in optical sequence.This means that a light beam impinging on perpendicular on the eyeprotection shield passes both liquid crystal cells at least in thelight-transmission-state. In such an embodiment one polarizer may bearranged between the two liquid crystal cells and the so formed sandwichof the two liquid crystal cells may be arranged between further twopolarizers. Accordingly, such an embodiment has three polarizers and twoliquid crystal cells. This is advantageous to provide a maximizeddarkening effect in the dark-state and a sufficient light transmissionstate in the light-transmission-state.

The eye protection shield is preferably connected to a sensor and acontrol circuit. In particular, the control circuit is preferablyelectrically connected to the first and second electrode layer of theliquid crystal cell for powering liquid crystal cell dependent on asignal provided by the sensor. The control circuit may for example applya voltage to the first and second electrode layer for causing the liquidcrystals to orient in a particular orientation, or switch off thevoltage so that the liquid crystals reset to their preferred orientationprovided by the first and second alignment layer. Thereby the darkeningfilter is switched between the light-transmission-state or thedark-state. Preferably, the sensor, the control circuit and thedarkening filter cooperate such that light of a certain minimumintensity received by the sensor causes the darkening filter to switchin the dark-state, and light of an intensity below that minimumintensity causes the darkening filter to switch in thelight-transmission-state.

In a further embodiment the eye protection shield has a band pass filterfor attenuating the infra-red (IR) and ultra-violet (UV) wavelengthcomponents from high-intensity incident light. The band pass filter canbe an interference filter that reflects the IR radiation and absorbs theUV-A, -B and -C components of the incident light.

In one embodiment the curved eye protection shield the protective coveris an “inner protective cover”. The inner protective cover is arrangedwith the outer surface facing the inner surface of the darkening filter.Alternatively, the protective cover may be an “outer protective cover”.The outer protective cover is arranged with the inner surface facing theouter surface of the darkening filter. It is noted that the inventionencompasses an eye protection shield having both, an inner and an outerprotective cover. In other words, the presence of an inner protectivecover does not exclude the additional presence of an outer protectivecover.

In such an embodiment the outer protective cover may havenon-equidistant inner and outer surfaces as described above orequidistant inner and outer surfaces as described in the following.

Accordingly, in one embodiment the eye protection shield further (inaddition to the inner protective cover having non-equidistant inner andouter surfaces) has an outer protective cover being arranged on oradjacent the outer surface of the darkening filter. The outer protectivecover may be provided to protect the darkening filter from dust andsplashes of hot or glowing material during welding. Preferably, theouter protective cover is removably attached to the darkening filter.Therefore, the outer protective cover can be replaced if necessary. Theouter protective cover may have a major inner surface and, oppositethereof, a major outer surface. The inner and outer surface of the outerprotective cover may be equidistant. In other words, a thickness definedbetween the inner and outer surface of the outer protective cover ispreferably uniform. The inner and outer surface of the outer protectivecover preferably form surfaces of a portion of the outer protectivecover which serve for the user, for example a welder, to see throughduring use. This portion of the outer protective cover therefore mayalso be referred to the “see-through portion of the outer protectivecover”. The outer protective cover may have further portions, such asone or more structures for stiffening the outer protective cover or formounting the outer protective cover within the eye protection shield,for example. Such further portions are typically not used for seeingthrough and further may not have equidistant inner and outer surfaces.

Alternatively, in one embodiment the eye protection shield further (inaddition to the outer protective cover having non-equidistant inner andouter surfaces) has an inner protective cover being arranged on oradjacent the inner surface of the darkening filter. Again, the innerprotective cover may be provided to protect the darkening filter fromdust and splashes of hot or glowing material during welding. Preferably,the inner protective cover is removably attached to the darkeningfilter. Therefore, the inner protective cover can be replaced ifnecessary. The inner protective cover may have a major inner surfaceand, opposite thereof, a major outer surface. The inner and outersurface of the inner protective cover may be equidistant. In otherwords, a thickness defined between the inner and outer surface of theinner protective cover is preferably uniform. The inner and outersurface of the inner protective cover preferably form surfaces of aportion of the inner protective cover which serve for the user, forexample a welder, to see through during use. This portion of the innerprotective cover therefore may also be referred to the “see-throughportion of the inner protective cover”. The inner protective cover mayhave further portions, such as one or more structures for stiffening theinner protective cover or for mounting the inner protective cover withinthe eye protection shield, for example. Such further portions aretypically not used for seeing through and further may not haveequidistant inner and outer surfaces.

The refractive power for the purpose of the present specification ismeasured in accordance with Standards EN 166:2001 (E) and EN 167:2001(E).

In a further aspect the invention relates to a welding protector. Awelding protector may be a welding mask or welding helmet, for example.The welding protector preferably comprises the curved eye protectionshield of the invention and a non-transparent head protection shield.The head protection shield preferably at least comprises a faceprotection portion. The head protection shield may comprise a furtherportion for protecting further parts of a wearer's head. The headprotection shield preferably forms a window which is closed by thecurved eye protection shield.

In a further embodiment the welding protector further comprises aheadband for retaining the welding protector on a wearer's head. Thehead protection shield is preferably pivotally suspended relative to theheadband. Thus, the head protection shield can be swiveled between alower position in which the head protection shield protects a wearer'sface, eyes and eventually further parts, and an upper position in whichthe head protection shield is lifted away from the wearer's face.Therefore, a wearer does not need to put off the welding protector foraccessing her or his face, for example.

In a further aspect the invention relates to a method of retrofitting awelding protector which has a curved eye protection shield. The eyeprotection shield comprises an electrically switchable darkening filterhaving an eye facing major inner surface and, opposite thereof, a majorouter surface. The inner and outer surface of the darkening filter areequidistant. The method comprises the steps of (i) providing aprotective cover having a major inner surface and further a major outersurface, wherein the inner and outer surface of the protective cover arenon-equidistant (as specified herein), and (ii) mounting the protectivecover relative to the darkening filter such that the outer surface ofthe protective cover faces the inner surface of the darkening filter orsuch that the inner surface of the protective cover faces the outersurface of the darkening filter.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a welding protector according to anembodiment of the invention; and

FIG. 2 is a top view on an eye protection shield according to anembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a curved eye protection shield 1 for welding protection.The eye protection shield 1 has an electrically switchable darkeningfilter 10, an inner protective cover 20 and an outer protective cover30.

The darkening filter 10 is an automatic darkening filter, in the exampleis based on a liquid crystal cell. The darkening filter 10 iselectrically switchable between a light-transmission-state and adark-state. When switched in the dark-state, the darkening filter 10blocks a significant amount of light from being transmittedtherethrough. This enables a user to observe a welding arc by seeingthrough the darkening filter 10 without risking to be exposed to harmfullight radiation from the welding arc. In the light-transmission-statethe darkening filter 10 permits a significant amount of light to betransmitted therethrough. Thus, the darkening filter 10 in thelight-transmission-state allows the user to see under ambient lightconditions (in the absence of the welding arc).

The darkening filter 10 has an eye facing major inner surface 11 and,opposite thereof, a major outer surface 12. Further, the innerprotective cover 20 has a major inner surface 21 and further a majorouter surface 22. The inner protective cover 20 is provided forarrangement on or next to the inner surface 11 of the darkening filter10. In the example the inner protective cover 20 is attached at a spacerelative to the inner surface 11 of the darkening filter 10. Severalways of attaching the inner protective cover 20 to the darkening filter10 are possible, for example by individually mounting the darkeningfilter 10 and the inner protective cover 20 in a welding protector (notillustrated).

The inner and outer surface 11, 12 of the darkening filter 10 areequidistant. In the example, the inner and outer surface 11, 12 of thedarkening filter 10 each have a cylindrical shape. Therefore, theequidistant inner and outer surface 11, 12 are concentric relative toeach other. Due to the curvature of the cylindrical shape the darkeningfilter 10 has a certain refractive power with respect to a wearerviewing through the darkening filter 10. This is because light passingthrough the darkening filter 10 at angles other than perpendicular tothe inner and outer surface 11, 12 are deflected by the darkening filter10.

The inner and outer surface 21, 22 of the inner protective cover 20 arenon-equidistant. In particular the inner and outer surface 21, 22 areshaped to compensate for the refractive power of the darkening filter10. In the example, the inner and outer surface 21, 22 are eachcylindrical but not concentric. In particular, the inner and outersurface 21, 22 are in an off-center relationship relative to each other.The centers of the inner and outer surface 21, 22 of the innerprotective cover 20 are offset relative to each other in a dimensionperpendicular to the inner and outer surface 21, 22. Further, the innerand outer surface 21, 22 are arranged such that the center of the outersurface 22 is arranged between the center of the inner surface 21 andthe inner protective cover 20. Accordingly, the inner and outer surface21, 22 extend non-equidistant relative to each other, in a mannerproviding a refractive power that compensates for the refractive powerof the darkening filer 10.

The outer protective cover 30 in the example has a major inner and amajor outer surface 31, 32 which extend equidistant to each other. Inparticular, the inner and outer surface 31, 32 are cylindrical andconcentric relative to each other. In another example the outerprotective cover 30 may extend non-equidistant to compensate for arefractive power of the darkening filter 10. In still another examplethe refractive power of the darkening filter 10 may be compensated by acombination of both, the inner and outer protective cover 20, 30.

The outer surface 12 of the darkening filter 10 is based on acylindrical shape which is defined by a radius of 90.1 mm and the innersurface 11 of the darkening filter 10 is based on a cylindrical shapewhich is defined by a radius of 89 mm. The inner and outer surface 11,12 of the darkening filter 10 are concentric. The refractive power ofthe darkening filter 10 is −0.044 l/m. The inner and outer surface 21,22 of the inner protective cover 20, are each based on a cylindricalshape which is defined by a radius R of 85 mm. The inner and outersurface 11, 12 are in an off-center relationship to each other with theoffset D of the off-center relationship being 1.7 mm. Accordingly, themaximum thickness T1 is 1.7 mm. T2 indicates an area in which the innerprotective cover has a smaller thickness than 1.7 mm. The refractivepower of the inner protective cover 20 in the example is 0.051 l/m.Further, in this embodiment the outer surface 32 of the outer protectivecover 30 is based on a cylindrical shape which is defined by a radius of91 mm and an inner surface 31 of the outer protective cover 30 is basedon a cylindrical shape which is defined by a radius of 90.25 mm. Theinner and outer surface of the outer protective cover are concentric.The refractive power of the outer protective cover is −0.034 l/m. Thecombination of the inner protective cover 20, the darkening filter 10and the outer protective cover 30 (as illustrated) thus has a totalrefractive power of −0.027 l/m. The absolute value of the totalrefractive power of the combination of the inner protective cover 20,the darkening filter 10 and the outer protective cover 30 is lower thanthe absolute value of each of the inner protective cover 20, thedarkening filter 10 and the outer protective cover 30 individually.

Other dimensions are possible as appropriate. The refractive power ofthe eye protection shield or its components may be calculated inaccordance with Gullstrand's afocal lens formula:

${\frac{1}{f} = {( {n - 1} )\lbrack {\frac{1}{R_{1}} - \frac{1}{R_{2}} + \frac{( {n - 1} )d}{{nR}_{1}R_{2}}} \rbrack}},$

In which “n” is the refractive index of the material of the eyeprotection shield and its components, R1 is the radius of the outersurface, R2 is the radius of the inner surface and d is the thickness ofthe eye protection shield or its components. It is noted that R2 for theeye protection shield or its components is a negative value because itrefers to the radius of a concave surface, whereas R1 refers to theradius of a convex surface.

1. A curved eye protection shield for welding protection, comprising anelectrically switchable darkening filter and a protective cover, whereinthe protective cover is removably attached to the darkening filter, thedarkening filter having a refractive power, an eye facing major innersurface and, opposite thereof, a major outer surface, and the protectivecover having a major inner surface and, opposite thereof, further amajor outer surface, wherein one of the inner and outer surface of theprotective cover faces the respective outer or inner surface of thedarkening filter, and wherein the inner and outer surface of theprotective cover are shaped to compensate for the refractive power ofthe darkening filter.
 2. The curved eye protection shield of claim 1,wherein an absolute value of a total refractive power of a combinationof an inner protective cover, the darkening filter and an outerprotective cover is lower than the absolute value of each of the innerprotective cover, the darkening filter and the outer protective coverindividually.